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Electronic Flora of South Australia Family Fact Sheet
Phylum Phaeophyta
Thallus (sporophyte) comparatively large, usually 1–5 (–30) m high, clearly differentiated into a holdfast (usually with haptera), a cylindrical to compressed stipe, and flattened, often branched, lamina, and in some genera with pneumatocysts (vesicles). Growth intercalary, in the region (the transition zone) at the top of the stipe or base of the lamina and also at the base of laterals when present, or below the apices of long fronds and involving lengthwise splitting to form elongate blades. Thallus increasing in thickness by a surface meristoderm. Structure polystichous, internally differentiated into an inner medulla of filaments or hyphae (in some taxa with some similar to sieve tubes and conductive) and an outer cortex of several layers of isodiametric to elongate cells becoming progressively smaller to the outside, with a surface meristoderm. Phaeoplasts numerous in outer cells, discoid, generally without pyrenoids. Phaeophycean hairs absent.
Gametophytes microscopic, filamentous, branched.
Reproduction: The sporophyte by unilocular meiosporangia (intermixed with clavate paraphyses) in extensive sori on the lamina or on sporophylls, producing 16–64 motile zoo(meio)spores. The gametophytes dioecious, oogamous.
Life history diplohaplontic with a large, conspicuous sporophyte and microscopic filamentous gametophytes.
Taxonomic notes: This is essentially a cold-water order, richly developed in the cold temperate and Arctic waters of the northern hemisphere, less so in the southern hemisphere and absent from the Antarctic (Moe & Silva 1977a).
Four families are recognised, two of which (with three genera) occur on southern Australian coasts where they can be conspicuous elements of the mid to upper sublittoral zones.
References:
MOE, R.L. & SILVA, P.C. (1977a). Antarctic marine flora: uniquely devoid of kelps. Science 196, 1206–1208.
The Marine Benthic Flora of Southern Australia Part II complete list of references.
Publication:
Womersley, H.B.S. (14 December, 1987)
The Marine Benthic Flora of Southern Australia
Part II
©Board of the Botanic Gardens and State Herbarium, Government of South Australia
KEY TO FAMILIES OF LAMINARIALES
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1. Longitudinal splits extending through the transition zone of young or mature fronds, with several to numerous fronds or blades, each with its own stipe, from the holdfast; sori on blades borne on the holdfast | LESSONIACEAE |
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1. Longitudinal splits absent; the holdfast bearing a single stipe and blade, with laterals arising from the transition zone; sori on the central blade or on the laterals | ALARIACEAE |
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Email Contact: State Herbarium of South Australia |
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